面試題 04.04. 檢查平衡性

面試題 04.04. 檢查平衡性

計算子樹的高度差<2，一次遍歷的話出現不平衡直接返回-1

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isBalanced(TreeNode* root) {
        return judge(root)!=-1;
    }
    int judge(TreeNode* root){
        if(root==NULL) return 0;
        int left = judge(root->left);
        int right = judge(root->right);
        if(left==-1 || right==-1) return -1;
        return abs(left-right)<2?max(left, right)+1:-1;
    }
};